This patent application claims priority under 35 U.S.C. 119 (a)-(d) of German Patent Application No. 100 32 882.2, filed on Jul. 6, 2000.
The invention relates to an apparatus for utilising solar energy which substantially consists of a mirror construction with a large number of reflector mirrors and heat exchanger collecting tubes on which the radiation energy of the sun is focussed.
An apparatus of this type, also known as solar heating apparatus, is known, for example, from the Offenlegungsschrift WO 99/42765. In the known apparatus, a moving mirror construction and at least one collector tube which is arranged parallel to the mirror constructions oppose one another on a frame. The solar radiation is conveyed to the collector by a plurality of flat mirrors which are arranged below the collector and are each arranged at a suitable angle to the incident solar radiation. The individual flat mirrors are connected via a mirror holder to a drive which automatically tracks the mirrors following the solar altitude. The solar heating apparatus known from WO 99/42765 has a number of drawbacks. The schematic arrangement of the drive of the mirror holder shown in the Offenlegungsschrift does not have the precision of such a drive demanded in practice. In fact, a maximum permitted deviation of the mirror orientation desirably of xc2x10.10 with respect to the optimum reflection angle is used as a basis in flat mirror carriers which are typically up to 200 m long.
Depending on the method of construction, moreover, the weight of the mirrors causes an enormous force which acts on the mirror holder drive and changes according to the dependency of the position of the mirrors on the mirror holder carrier.
When the solar heating apparatus is used in an external environment with a desert climate, there is a particular need to design the moving parts of the apparatus, on the one hand, precisely with respect to temperature variations. On the other hand, moving parts and other parts are to withstand stresses due to dust and sand, in particular in cylinder and roller parts of the apparatus. In particular, it should be possible to design the rolling bearings without lubrication as the fine sand can cause the lubricant to stick. It should also be possible to reduce friction in the bearings by the selection of suitable materials.
Whereas other known apparatuses for utilising solar energy have, for example, a mirror construction on parabolic large-area reflector elements, the solar heating apparatus described hereinafter is based on flat small area mirror elements.
As described, carriers and mirror elements have a considerable weight, so considerable forces are required to achieve a deflection of the mirrors with mirror carriers having a length of up to 200 m and more.
It is a further object of the invention to design the bearings arranged along the mirror carriers for rotation of the mirror carriers in such a way that they compensate the thermal expansion occurring due to the temperature difference between day and night.
In accordance with the present invention, there is provided an apparatus for utilising solar energy comprising:
(a) a plurality of movable mirrors (3) which are arranged in parallel next to one another, are orientable according to the solar altitude, and are fastened on carriers (10, 10xe2x80x2);
(b) at least one stationary collector (14) for absorbing the radiation reflected by the mirrors (3);
(c) a drive means for rotating the mirrors (3) and carriers (10, 10xe2x80x2) in order to orientate the mirrors (3) in such a way that the solar radiation impinging on the mirrors is reflected onto the collector (14); and
(d) a framework (15) supporting said mirrors (3), said carriers (10, 10xe2x80x2), said stationary collector (14) and said drive means
wherein the mirrors (3) of the carriers (10) are mounted rotatably about an axis of rotation, that is parallel to the length of the mirrors, in such a way that the weight of the mirrors (3) and the weight of the carriers (10) are substantially in equilibrium in any position about said axis of rotation.
The features that characterise the present invention are pointed out with particularity in the claims, which are annexed to an form a part of this disclosure. These and other features of the invention, its operating advantages and the specific objects obtained by its use will be more fully under stood from the following detailed description and the accompanying drawings in which embodiments of the invention are illustrated and described.
Unless otherwise indicated, all numbers ore expressions, such as those expressing structural dimensions, etc, used in the specification and claims are to be understood as modified in all instances by the term xe2x80x9cabout.xe2x80x9d